Heating unit



M. M. KOHN July 19, 1927.

HEATING UNIT 2 Sheets-Sheet 2 lnx/enfer.'

Filed Feb. 23- 1921 Patented July 19, 1927.

UNITED STATES METO M. KOEN, OF NW'YORK, N. Y.

mamme UNIT.

appmaaon mea February 2s, 1921. sena no. 447,122.

The invention relates to an easilyremovable, insertable and replaceable heating element for use in electrical toasters and de' vices used for cooking and heating purposes,

such for example, as described and claimed in 'my co-pendingapplication Serial No. 440,641, filed January 28, 1921.

My heating element consists preferably of a thin plate carrying the resistance element and :radiating heat generated thereby from both sides thereof.

M invention: is capable of various modicat1ons,'a numberof which are described and illustrated herein. Referring to the drawings: y.

Fig. 1 is a longitudinal section of one embodiment. i

Fig. 2 is a crosssection thereof. Fig. A3 is a longitudinal section of another embodiment.

Fig. 4 is a cross section thereof. Fig. 5 is a plan view 0f another embodlment. Fig. 6 is across section thereof. Fig. 7 is a plan view of a different 'embodiment, s Fig. 8 is a cross section thereof.` Fig. 9 is a sectional view of still another embodiment. 1 Referringl to Figs. 1 and 2, 10 designates Asuitable plastic insulating heat resisting material, within which is embedded coiled wire 11' having suitable` terminals 12. The ymaterial 1 0 is. preferably of such character as to have low electrical conductivity, or none at all. The coils 11 are wholly em,- bedded withinthe material 10 and serve to convert the electrical energy supplied thereto into heat. Within the insulating material are sleeves 13 adapted to receive pins 14 having suitable knurled heads 15 at one end and screw threads 16 or other'suitable attaching means for fastening and connecting the heating elements within the device. in which they are to supply heat, at the other end, as described in my application above referred to. It may, at times, be'desirable to have a very thin heating element, in which 'case the coils 11 .may be flattened as shown at 11, Figs. 3 and 4.

The modification shown in Figs. 5 and 6" is similar to those already illustrated, except that instead of the coils of resistance wire,

in one direction (as illustrated at on one side of the sheet of insulating material 51,

-it being'understood, of course, that the wires this resistance wire is wound back and forth?.

for example ofmica, and then back alndforth` in the other direction on the other side of said insulating material, as illustrated at 52,

on one side of the sheet may constitute a ,separate coil from the wires on the other, or

they may constitute one continuous coil.

The modification illustrated in Figs. 7 and .8 is like that of Figs. 5 and 6, except that 65 perforations are provided in the lastic heat conducting, but electrically insul)ating, mass, and may, if desired, also be provided -in the mica sheet 51.5 These perforations,

which may have any desired form, for example, rectangular, are preferably provided within the material opposite the rectangles formed by the criss-crossing wire, so that thebeneit 4of the perforations may be had. without exposing the resistancevwire at any point.

The perforations are advantageous in that .they permit of increased circulation of air,l

and when the device describedinv-my applicatmn above mentioned .lis to ibe lused. merely to heat the air, the perforated modiiica'tion` has a decidedV advantage over the other embodiments. l l' These heating units vare .very useful in v such a device as that described and claimed in my application above referred to where' in the material to be heated is heatedfon both sides .and practically over its' entire surface, thus permitting the-heating units to be'operated at a temperature much lower 90 than is-usually the case.' In fact, very oo'd results are obtained in my apparatus w ere the temperature of the heating units during operation is maintained so low that there is no visible glowing, and I can obtain vvery good cooking and-toasting results in my apparatus when operating ,the heating units at a temperature as lowas 400 to 500C' F` In view of the fact that the temperature of the heating units maybe maintained as low as above stated, I can use ordinary iron wire as my resistance element, it being understood, of course, that I may use any desired resistor. Iron wire, as a resistor, when operated at' temperatures high enough to roduce glowing, lasts but a very short time, ut'whenope'rated at a, temperature below glowing temperature' or when operated at the low temperatures of.400 ,to 500 F., orV even .up`to 800 F.,.'which is permitted by my invention, will-last. for a ve longtime.

In' the modification illustratdd in Fig. 9,

vof the 'perforations a conducting sheet, strip or plate 91 is bent back and forth to form a multiplicity of connected laminae, each of which is insulated from the adjacent lamin by electrically insulating sheets, strips or plates 92; the whole may then be embedded in a plastic mass.

For the plastic material I find most suitablefa composition consisting of silicon, 4 to 7 parts, carborundum, preferably amorphous, 85 to 90 parts, graphite (low grade) 1 to 2` parts, and commercial sodium silicate solution suilicient to make a paste. The previously formed resistor may be embedded in this paste,.as may the sleeves 13. The whole is then dried and heated, and then treated with a solution of zirconium silicate to form a glaze thereon. The strength ,of the zirconium silicate solution is more or less immaterial, and it may be varied from a thi-n to a thick liquid.

My resistance-elements may be in the form of wire, or in the -orm of lat sheets, which may beA perforated, or may be'in the form of very thin ribbon wound edgewise.

' I claim:

-Y 1. A resistance element comprising a thin dielectric plate having a group ofuniformly spaced rectangular perforations and a resistance `member completely embedded in the material of the. late 'to surround each ereln.

, ture.

2. A resistance element comprising a thin dielectric plate having transverse perforations therethrough, a resistance member embedded in said plate circumjacent each perforation, and means to support the plate, said means bein disposed adjacently parallel the edges o? the plate beyond the perforations.

' 3. A resistance element comprising a conductor embedded in a mass consisting of silicon, carborundum, graphite and sodium silicate.

4. A resistance element comprising a conductor embedded in a thin sheet of a mass consisting of silicon, 4 to 7 parts, carborundum, 85 to `90 parts, graphite, 1 to 2 parts, and sodium silicate.

5. 'A resistance element comprising a conductor embedded in a mass consistin of silicon, carborundum, graphite and sodium silicate, the sheet being coated withl zirconium silicate. A

6. A resistance material comprising a conductor embedded in Ya thin sheet of a mass consisting of 4 to 7 parts of silicon, 85 to 90 parts of carborundum, graphite 1 to 2V parts, and sodium silicate, the sheet being coated with zirconium silicate. y

In testimony whereof I .aiiix my signa MILTON `M. KOHN. 

